Sensor circuit for detecting the setting of an integrated circuit

ABSTRACT

Methods and apparatus selecting settings for circuits according to various aspects of the present invention may operate in conjunction with a measurement element connected to the circuit. The circuit may include a voltage source adapted to supply a voltage to the measurement element. The voltage may be substantially independent of the characteristics of the measurement element. The circuit may further include a measurement sensor responsive to a current in the measurement element. The measurement sensor may generate a control signal according to the current in the measurement element.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.12/639,187, filed 16 Dec. 2009, which claims the benefit of U.S.Provisional Patent Application No. 61/122,926, filed Dec. 16, 2008, andincorporates the disclosure of such applications by reference.

BACKGROUND OF INVENTION

Many integrated circuits provide functions with multiple settings thatcan be selected, such as after the integrated circuit has been placed ona printed circuit board or otherwise secured. Conventional methods mayuse digital mechanisms for selecting the settings. The integratedcircuit pin may have two states (logic high or logic low) or threestates (logic high, a mid voltage state and a logic low state). Varioussystems have been deployed using resistor-based circuits for selectingone of multiple settings in conjunction with a direct current be appliedto the terminal of the integrated circuit to flow through themeasurement resistor with a subsequent quantizing of the voltageproduced.

SUMMARY OF THE INVENTION

Methods and apparatus for selecting settings for circuits according tovarious aspects of the present invention may operate in conjunction witha measurement element connected to the circuit. The circuit may includea voltage source adapted to supply a voltage to the measurement element.The voltage may be substantially independent of the characteristics ofthe measurement element. The circuit may further include a measurementsensor responsive to a current in the measurement element. Themeasurement sensor may generate a control signal according to thecurrent in the measurement element.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconnection with the following illustrative figures. In the followingfigures, like reference numbers refer to similar elements and stepsthroughout the figures.

FIG. 1 representatively illustrates an electronic system comprising anintegrated circuit and a measurement element.

FIG. 2 illustrates an integrated circuit including a voltage source anda measurement sensor.

FIG. 3 illustrates an integrated circuit including an exemplary voltagesource, an exemplary measurement sensor, and an internal controlresistor.

FIG. 4 illustrates an integrated circuit including an external controlresistor.

FIG. 5 illustrates an integrated circuit including a measurement sensorcomprising a current source, a capacitor, and a buffer.

FIGS. 6 and 8 illustrate integrated circuits including correctioncircuits.

FIG. 7 illustrates an integrated circuit including a measurement sensorcomprising a comparator, a digital-to-analog converter, and a controlcircuit.

FIG. 9 illustrates an exemplary method for selecting a setting for anintegrated circuit.

Elements and steps in the figures are illustrated for simplicity andclarity and have not necessarily been rendered according to anyparticular sequence. For example, steps that may be performedconcurrently or in different order are illustrated in the figures tohelp to improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention may be described in terms of functional blockcomponents and various processing steps. Such functional blocks may berealized by any number of hardware or software components configured toperform the specified functions and achieve the various results. Forexample, the present invention may employ various resistors, voltagesupplies, measurement sensors, and the like, which may carry out avariety of functions. In addition, the present invention may bepracticed in conjunction with any number of circuits and systems, andthe integrated circuit system described is merely one exemplaryapplication for the invention. Further, the present invention may employany number of techniques for generating voltages, measuring currents,generating signals, and the like, such as disclosed in U.S. Pat. Nos.6,894,501 and 7,091,736 to Flasck et al. and U.S. Pat. No. 6,122,296 toShih.

Methods and apparatus for selecting settings for a circuit according tovarious aspects of the present invention may operate in conjunction withan electronic system including integrated circuits. Referring now toFIG. 1, an exemplary electronic system 100 may comprise a component,such as an integrated circuit 110 or the like, and a measurement element112. Selecting a measurement element 112 having particularcharacteristics determines a particular setting for the integratedcircuit 110.

For example, the integrated circuit 110 may be adapted to operate inconjunction with multiple settings, such as more than two settings, morethan three settings, or more than four settings. The integrated circuit110 may comprise any appropriate integrated circuit that operates inconjunction with different settings according to signals that may beselectively adjusted. In one embodiment, the integrated circuit 110comprises a switching voltage regulator. The settings may designate anysuitable characteristics, such as operational modes, operatingenvironments, switching frequencies, set points, droop levels, digitalcompensation modes, or other user-selectable settings. An example of aselected setting may be a bus address value for the integrated circuit110 to uniquely distinguish the integrated circuit 110 from otherintegrated circuits sharing the digital bus.

The integrated circuit 110 may include a functional module 108 and/orother circuits that receive a control signal corresponding to aquantized state and determine the desired setting based on the quantizedstate. The integrated circuit may be adapted to provide multiple controlsignals to various functional modules 108 or other circuits. Thefunctional module 108 implements the selected setting represented by thecontrol signal.

The setting of the integrated circuit 110 may be determined according tothe measurement element 112. The measurement element 112 controls thesetting used by the integrated circuit 110, and the measurement element112 may be selected according to the desired setting. For example, themeasurement element 112 may comprise a single resistor, and theresistance of the resistor may be selected according to the desiredsetting. In one embodiment, the resistor may have a range of resistancevalues representing different settings, such as from about 1K ohms to10K ohms. A suitable resistor may be a variable-resistance resistor or aresistor selected from an array of resistors having different values.The measurement element 112 may, however, comprise any appropriateelement that may be varied according to the desired selection. Forexample, the measurement element 112 may be implemented as one or moreresistors, capacitors, inductors, current sources, voltage sources, andthe like.

The measurement element 112 may communicate with the integrated circuit110 or other elements in any suitable manner to communicate the desiredsetting. In the present embodiment, the measurement element 112 iscoupled to the integrated circuit 110 via a conventional terminal, suchas a pin or pad.

The integrated circuit 110 may be configured to sense a characteristicof the measurement element 112 and use the indicated setting. Referringto FIG. 2, an exemplary integrated circuit 110 may include a sensorcircuit 114 adapted to sense the relevant characteristic of themeasurement element 112 and generate a corresponding control signal. Forexample, the sensor circuit 114 may comprise a voltage source 116 and ameasurement sensor 118. The voltage source 116 may be adapted to supplya voltage that is independent of the measurement element 112 to theterminal connected to the measurement element 112. The measurementsensor 118 may be responsive to a current in the measurement element 112and adapted to produce a control signal according to the current, suchas by determining a resistance, impedance, or capacitance of themeasurement element 112. The control signal may represent the desiredsetting as indicated by the particular measurement element 112, whereeach setting is represented by a different value of the measuredcharacteristic in the measurement element 112 and a different controlsignal generated by the measurement sensor 118. The functional module108 or other circuit receiving the control signal may then implement theselected setting.

In various systems employing a current source instead of a voltagesource, the voltage that appears at the terminal of the integratedcircuit 110 is a function of the measurement element 112, such as anexternal resistor value. In the present embodiment, the voltage on theterminal is substantially independent of the measurement element 112.Further, the current flowing through the measurement element 112 is afunction of the external measurement resistor value or othercharacteristic of the measurement element 112 and may be measured toselect one of multiple settings. Accurate DC voltages are easier, suchas simpler and/or cheaper, to generate than accurate DC current inintegrated circuits, such as when high precision resistors are notavailable. Precision voltages based on bandgap techniques may be readilycreated in most integrated circuit fabrication technologies. Further,voltages are generally easier to trim or adjust to achieve high accuracyin the presence of circuit variations related to the manufacturingprocess. In addition, internal resistance variation can be easilyaccounted for by adjusting V_(ref).

The sensor circuit 114 facilitates significantly more than two or threestates to be selected with a single pin. Embodiments in which eight orsixteen or even more settings could be selected based on an externalresistor value are possible. Consequently, a reduced number of pins maybe used to select the desired settings.

The voltage source 116 may comprise any suitable source for generating asubstantially constant or otherwise controllable voltage, such as toapply a known voltage to the measurement element 112 that is independentof the measurement element 112 characteristics. In one exemplaryembodiment, the measurement element 112 comprises an external resistor120 coupled to the terminal of the integrated circuit 110. The voltagesource 116 generates a constant known voltage across the externalresistor 120. In one embodiment, the voltage may be selected from commonvoltages in the environment, such as 1 volt or 5 volts in amicroprocessor-based system. The voltage generated by the exemplaryvoltage source 116 and applied to the terminal is nominally independentof the resistance of the external resistor 120. In another embodiment,the measurement element 112 may comprise a capacitor. The voltage sourcemay deliver a constant known voltage to the capacitor, and the sensorcircuit 114 may measure the interval required for the current level inthe capacitor to cross a selected threshold.

The voltage source 116 may comprise any suitable voltage source forgenerating a substantially constant and/or independent voltage. Forexample, referring to FIG. 3, the voltage source 116 may comprise asensor, such as a conventional operational amplifier (op amp) 122, and amodulator, such as a switch or amplifier for example a conventionalMOSFET 124. The op amp 122 receives a reference voltage V_(ref) at anoninverting input and generates an output voltage at an inverting inputthat is approximately equal to the reference voltage which is alsosupplied to the external resistor 120. The op amp serves to drive thedifference signal between the reference voltage and the output voltageto approximately zero.

The output of the op amp 122 drives the modulator to control the signalapplied to the external resistor 120. For example, the gate of theMOSFET 124 may have a terminal connected to the external resistor 120and a second terminal connected to a relatively high voltage V_(dd). Theop amp 122 drives the MOSFET 124 such that the voltage applied to theexternal resistor 120 is always driven towards the value of thereference voltage V_(ref). Consequently, the voltage at the integratedcircuit terminal is approximately equal to V_(ref). The current flowingthrough the external resistor R_(ext), (I_(ext)) is thenV_(ref)/R_(ext). Any suitable voltage source, however, may beimplemented for applying the desired voltage to the measurement element112.

The measurement sensor 118 may be responsive to the current in themeasurement element 112 and adapted to produce the control signalaccording to the current. The control signal may represent the desiredsetting corresponding to one or more relevant characteristics of theparticular measurement element 112. The measurement sensor 118 maycomprise any suitable sensor for responding to the current in themeasurement element 112 and directly or indirectly adjusting the controlsignal based on the current in the measurement element 112. For example,referring to FIG. 2, the measurement sensor 112 may comprise a currentsensor 126 and an analog-to-digital converter (ADC) 128. The currentsensor 126 may comprise a conventional current sensor configured togenerate an analog electrical signal corresponding to the current in themeasurement element 112. In the present embodiment, the current sensor126 measures the current in series with the external resistor 120 andgenerates a corresponding analog signal.

The analog signal generated by the current sensor 126 is provided to theADC 128, which quantizes the analog signal to generate a correspondingdigital signal. In the present embodiment, a current flows through theexternal resistor 120 that is digitized by the ADC 128 to determine aquantized state. The ADC 128 may comprise any appropriate system forgenerating a digital signal according to an analog signal, such as aconventional ADC. The control signal may comprise the digital output ofthe ADC 128.

The digital control signal may be provided to any appropriate system forimplementing the indicated settings according to the control signal,such as the functional module 108 within the integrated circuit 110 thatimplements one of the possible settings according to the control signal.In alternative embodiments, the analog signal generated by the currentsensor 126 may be provided directly to the functional module 108, forexample for functional modules that operate on analog inputs or includean ADC for converting the received signal. In an alternative embodiment,the measurement sensor 118 may comprise a voltage sensor in place of orin addition to the current sensor 126.

The measurement sensor 118 may be configured in any appropriate mannerand include any appropriate elements to respond to the current in themeasurement element 112 and produce the control signal according to thecurrent. For example, the current sensor 126 may comprise a currentmirror adapted to generate a current corresponding to a current in themeasurement element 112. In one embodiment, referring to FIG. 3, themeasurement sensor 118 comprises a current mirror 310 coupled to the ADC128. The current mirror 310 is connected to the MOSFET 124, such as tothe drain of the MOSFET 124, such that the current mirror 310 generatesan output current having a magnitude corresponding to the magnitude ofthe drain-source current of the MOSFET 124. The current mirror 310 mayexhibit a current transfer function wherein the output current of thecurrent mirror 310 equals k times the input current to the mirror.

In the present embodiment, the output current of the current mirror 310is provided to an internal control resistor R_(int), forming a voltageacross the internal control resistor R_(int). The voltage across theinternal control resistor R_(int) is directly proportional to thecurrent flowing through the external resistor 120. In this embodiment,the voltage formed across the internal control resistor R_(int) equalsV₂=V_(ref)*k*R_(int)/R_(ext), which is directly proportional to thecurrent flowing through external resistor R_(ext) 120 and can beexpressed as V₂=I_(ext)*k*R_(int). The voltage is provided to the ADC128 to generate the digital control signal, producing a quantized signalto be provided to the functional module 108. The functional module 108receives the quantized state from the ADC 128 and determines a settingbased on the quantized state.

The signal corresponding to the current in the measurement element 112may be produced in any appropriate manner. For example, referring toFIG. 4, the internal control resistor R_(int) may be replaced orsupplemented with an external control resistor R_(trk). In this case, asecond terminal has been added to the integrated circuit 110 and thecontrol resistor R_(trk) that forms the voltage V₂ provided to the ADC128 has been placed external to the integrated circuit. In thisembodiment, V₂=I_(ext)*k*R_(trk) and is otherwise identical in functionto the embodiment of FIG. 3. The external control resistor R_(trk) mayhave less variation than resistors fabricated directly on the integratedcircuit, which may allow greater accuracy and allow more settings to bedetermined due to the increased accuracy of the sensing circuit 114.

Further, the control signal may be generated according to the current inthe external resistor 120 and/or quantized in any suitable manner. Forexample, referring to FIG. 5, the measurement sensor 118 may comprise acurrent source 510, a capacitor 512, and a buffer 514. In thisembodiment, the current source 510 and the capacitor 512 may beconnected to the node V₂. The reference current I_(ref) generated by thecurrent source 510 may be any appropriate current, such as a constantcurrent or a variable current dependent on another variable signalassociated with another circuit. The capacitor 512 integrates adifference current between the current generated by the current mirror310 (k*I_(sen)) and the current generated by the current source 510(I_(ref)). The buffer 514 creates a control signal having one of twooutput states according to whether k*I_(sen)>I_(ref) ork*I_(sen)<I_(ref). The control signal is transmitted to the functionalmodule 108 that determines a setting based on the state information.

In another embodiment, the measurement sensor 118 may measure thecurrent in the external resistor 120 and select a setting according tomultiple thresholds or criteria. For example, referring to FIG. 7, themeasurement sensor 118 may include a digital-to-analog converter (DAC)710, a comparator 712, and a control circuit 714. The control circuit714 may provide selected inputs to the DAC 710, such as by sequentiallyproviding a series of thresholds. The DAC 710 converts the digital inputto a corresponding analog signal, which is provided to the input of thecomparator 712.

The comparator 712 compares the DAC 710 output to the voltage at nodeV₂. The comparator 712 output may be provided to the control circuit714, for example to determine which threshold is closest to the voltageat node V₂. The control circuit 714 may decode the signal provided tothe DAC 710 along with the comparator 712 state to convert arepresentation of the current flowing through the external resistor 120(represented by the voltage at node V₂) to a specific quantized state.The functional module 108 receives the quantized state from the controlcircuit 714 and determines a setting based on the quantized state.

The integrated circuit 110 may comprise any other appropriatecomponents, elements, and systems for selecting the proper setting. Forexample, the integrated circuit 110 may include a correction circuit tocompensate for errors, such as offset and/or gain errors. The correctioncircuit may trim the output of one or more elements to improve theaccuracy of the sensor circuit 114. For example, referring to FIG. 6,the correction function may be implemented by a digital correctioncircuit 610 that compensates for offset and/or gain errors in the sensorcircuit path, inclusive of the ADC 128 function. The digital correctioncircuit 610 may receive a trim command, which may be stored on theintegrated circuit 110 and contains correction terms for offset and/orgain, such as in a look-up table. The correction term(s) for offset andgain may be combined with the output of the ADC 128 to form a correctedoutput. The corrected output is then used to determine a setting valuefrom multiple setting choices of the functional module 108 with highfidelity in the presence of circuit non-idealities.

The correction circuit may also be implemented for different types ofsensor circuits 114, and may be separate from or partially or fullyintegrated into the sensor circuit 114. For example, referring to FIG.8, the digital correction circuit 610 may be implemented in the systemshown in FIG. 7. The digital correction circuit 610 may compensate foroffset and/or gain errors in the sensor circuit path, including the DAC710. The correction term(s) for offset and/or gain may be combined withthe output of the control circuit 714 to form a corrected output. Thecontrol circuit 714 may decode the signal provided to the DAC 710 alongwith the comparator 712 state to convert a representation of the currentflowing through the measurement element 112 to a specific quantizedstate. A correction circuit may correct any appropriate signals. Forexample, an exemplary correction circuit may trim the input signalV_(ref) that appears at the measurement terminal connected to themeasurement element 112 to improve circuit accuracy in the presence ofcircuit non-idealities such as gain or offset errors.

In operation, referring to FIG. 9, the measurement element 112 may beselected to achieve the desired setting and connected to the integratedcircuit 110 (910). The sensor circuit 114 may apply a voltage to themeasurement element 112 at the terminal of the integrated circuit 110(912). The voltage applied to the measurement element 112 at theterminal may be nominally independent of the measurement element'scharacteristics. The sensor circuit 114 also generates a control signalaccording to the current flowing in the measurement element 112, therate at which the current in the measurement element 112 changes, orother characteristic affected by or associated with the measurementelement 112. The control signal may be provided to the functional module108 of the integrated circuit 110 to apply a setting according to thecontrol signal.

For example, in an embodiment where the measurement element 112 is theexternal resistor 120, the integrated circuit 110 may determine thesetting for a particular function according to the external resistor120. The voltage source 116 may apply a voltage to the external resistor120 that is independent of the resistance of the external resistor. Inthe present embodiment, the voltage applied to the external resistor 120remains constant for any resistance connected to the integrated circuit110.

The applied voltage generates a current flow in the external resistor120. The measurement sensor 118 directly or indirectly senses thecurrent in the external resistor 120 (914), such as by measuring thecurrent in a series path of the external resistor 120 or a voltage thatis associated with the current, and generates the control signalaccording to the measured current (916). The control signal may bequantized for processing by the functional module 108 of the integratedcircuit 110 to determine the desired setting (918). Each of the settingsmay be designated by a different value for the control signal, which isultimately controlled by the resistance selected for the externalresistor 120. The quantized control signal may be provided to thefunction module 108 (920), which may implement the selected setting asrepresented by the control signal (922).

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments. Various modifications andchanges may be made, however, without departing from the scope of thepresent invention as set forth in the claims. The specification andfigures are illustrative, rather than restrictive, and modifications areintended to be included within the scope of the present invention.Accordingly, the scope of the invention should be determined by theclaims and their legal equivalents rather than by merely the examplesdescribed.

For example, the steps recited in any method or process claims may beexecuted in any order and, unless otherwise noted, are not limited tothe specific order presented in the claims. Additionally, the componentsand/or elements recited in any apparatus claims may be assembled orotherwise operationally configured in a variety of permutations and areaccordingly not limited to the specific configuration recited in theclaims.

Benefits, other advantages and solutions to problems have been describedabove with regard to particular embodiments; however, any benefit,advantage, solution to problem or any element that may cause anyparticular benefit, advantage or solution to occur or to become morepronounced are not to be construed as critical, required or essentialfeatures or components of any or all the claims.

As used herein, the terms “comprise”, “comprises”, “comprising”,“having”, “including”, “includes” or any variation thereof, are intendedto reference a non-exclusive inclusion, such that a process, method,article, composition or apparatus that comprises a list of elements doesnot include only those elements recited, but may also include otherelements not expressly listed or inherent to such process, method,article, composition or apparatus. Other combinations and/ormodifications of the above-described structures, arrangements,applications, proportions, elements, materials or components used in thepractice of the present invention, in addition to those not specificallyrecited, may be varied or otherwise particularly adapted to specificenvironments, manufacturing specifications, design parameters or otheroperating requirements without departing from the general principles ofthe same.

The invention claimed is:
 1. An integrated circuit, comprising: aterminal for connecting to an external measurement element, the externalmeasurement element having a characteristic that indicates a setting ofthe integrated circuit; a sensor circuit comprising a voltage source anda measurement sensor, the voltage source configured to supply a voltageto the terminal that is independent of the characteristic of theexternal measurement element so that current flowing through theexternal measurement element responsive to the voltage is a function ofthe characteristic of the external measurement element, the measurementsensor configured to sense the current in the external measurementelement and generate a control signal based on the sensed current, thecontrol signal indicating the setting of the integrated circuit; and afunctional module configured to implement the setting indicated by thecontrol signal.
 2. The integrated circuit of claim 1, wherein thecharacteristic of the external measurement element is resistance, andwherein the measurement sensor is configured to determine the resistancebased on the current sensed in the external measurement element andgenerate the control signal based on the resistance.
 3. The integratedcircuit of claim 1, wherein the characteristic of the externalmeasurement element is impedance, and wherein the measurement sensor isconfigured to determine the impedance based on the current sensed in theexternal measurement element and generate the control signal based onthe impedance.
 4. The integrated circuit of claim 1, wherein thecharacteristic of the external measurement element is capacitance, andwherein the measurement sensor is configured to determine thecapacitance based on the current sensed in the external measurementelement and generate the control signal based on the capacitance.
 5. Theintegrated circuit of claim 1, wherein the measurement sensor isconfigured to detect the setting from a plurality of different settingsfor the integrated circuit and represented by different characteristicsof the external measurement element, based on the current measured inthe external measurement element.
 6. The integrated circuit of claim 1,wherein the external measurement element is a resistor and the voltagesource is configured to supply a constant voltage across the resistorvia the terminal that is independent of the resistance of the resistor.7. The integrated circuit of claim 1, wherein the external measurementelement is a capacitor and the voltage source is configured to supply aconstant voltage to the capacitor via the terminal that is independentof the capacitance of the capacitor, and wherein the measurement sensoris configured to measure an interval required for a current level in thecapacitor to cross a selected threshold.
 8. The integrated circuit ofclaim 1, wherein the voltage source comprises: an op amp configured toreceive a reference voltage at a non-inverting input of the op amp and afeedback voltage at an inverting input of the op amp, generate an outputvoltage approximately equal to the voltage supplied to the externalmeasurement element via the terminal, and drive a difference between thereference voltage and the output voltage to approximately zero; and amodulator configured to drive the external measurement element with thevoltage at the terminal responsive to the output voltage of the op amp.9. The integrated circuit of claim 8, wherein the modulator is a MOSFEThaving a first power terminal coupled to a current mirror, a secondpower terminal connected to the external measurement element via theterminal and a gate connected to the output of the op amp.
 10. Theintegrated circuit of claim 1, wherein the measurement sensor comprises:a current sensor configured to generate an analog electrical signalcorresponding to the current in the external measurement element; and ananalog-to-digital converter configured to convert the analog electricalsignal into the control signal.
 11. The integrated circuit of claim 10,wherein the current sensor is configured to measure a current in serieswith the external measurement element to generate the analog electricalsignal.
 12. The integrated circuit of claim 10, wherein the currentsensor comprises a current mirror configured to generate a currentcorresponding to the current in the external measurement element. 13.The integrated circuit of claim 12, further comprising an internalcontrol resistor connected to the current mirror and configured to forma voltage across the internal control resistor responsive to the currentgenerated by the current mirror, the voltage across the internal controlresistor being directly proportional to the current flowing in theexternal measurement element.
 14. The integrated circuit of claim 13,wherein the analog-to-digital converter is configured to convert thevoltage across the internal control resistor into the control signal.15. The integrated circuit of claim 12, wherein the analog electricalsignal converted by the analog-to-digital converter into the controlsignal is a voltage across an external control resistor connected toanother terminal of the integrated circuit, the voltage across theexternal control resistor being a linear function of the currentgenerated by the current mirror.
 16. The integrated circuit of claim 1,wherein the functional module is a switching voltage regulator.
 17. Theintegrated circuit of claim 16, wherein the setting implemented by theswitching voltage regulator is at least one of an operational mode ofthe switching voltage regulator, a switching frequency of the switchingvoltage regulator, a set point of the switching voltage regulator and adroop level of the switching voltage regulator.
 18. The integratedcircuit of claim 1, wherein the setting is a bus address uniquelyassociated with the integrated circuit.
 19. The integrated circuit ofclaim 1, wherein the measurement sensor is configured to measure acurrent in a series path of the external measurement element to sensethe current in the external measurement element.
 20. The integratedcircuit of claim 1, wherein the measurement sensor is configured tomeasure a voltage associated with a current in a series path of theexternal measurement element to sense the current in the externalmeasurement element.